Amid mutual statements of good will and a congressional request to President Reagan to steer clear of day-to-day negotiations, a House-Senate conference committee today began the task of reconciling the two houses' versions of tax revision.

The conference began its work as one of the groups that helped initiate the tax-revision movement released a report showing that 42 large, profitable companies paid no taxes from 1982 to 1985. The report, one of an annual series by Citizens for Tax Justice that helped to raise public ire against corporate tax evaders four years ago, found that 130 such firms had paid no taxes during at least one of those years.

The study said American Telephone & Telegraph Co., had paid no taxes during the four-year period despite pretax profits of $24.9 billion. Other companies with high profits and no tax bills were: E.I. du Pont de Nemours and Co., Boeing Co., General Dynamics Corp., Pepsico Inc. and General Mills Inc.

"Only by making these big corporations pay their fair share will middle-income taxpayers get a fair shake from the tax-reform bill now pending in Congress," said Citizens for Tax Justice tax director Robert S. McIntyre.

An AT&T spokeswoman, however, said the firm had paid $750 million in taxes during the four-year period, using the accounting method applied by Citizens for Tax Justice. The disagreement, she said, is over an settlement of a rate dispute in 1984 that was listed in the company's annual report as a tax refund even though no refund was paid.

"We are not a tax dodger," said the spokeswoman, Edith Herman.

At the conference, Senate Finance Committee Chairman Bob Packwood (R-Ore.) and others said Americans think the tax system is unfair because large companies do not pay their share and noted that the provisions of both the House and Senate bills would make it harder for companies to wipe out their tax bills.

"We are saying, companies that make millions of dollars in profits and pay no taxes will pay taxes," Packwood said.

Conferees took no votes yesterday, spending the day hearing exhortations from their colleagues and explanations of the provisions of both bills. House Ways and Means Committee Chairman Dan Rostenkowski (D-Ill.), who became chairman of the conference after being nominated by Packwood, said the panel may meet over the weekend of July 26-27 in order to complete its work by the scheduled deadline of Aug. 15.

Earlier, Packwood and Rostenkowski breakfasted at the White House with Reagan and asked him to refrain from commenting on the progress of the conference as it negotiates over which deductions to curtail and how far to reduce tax rates.

The president did not respond specifically to their request, but White House officials said the administration's positions will be conveyed by Reagan's chief tax writer, Treasury Secretary James A. Baker III, and his representatives.

Baker, appearing at the meeting of the 22-member conference committee, told Packwood and Rostenkowski he is "confident this conference can meld the best of both bills into a truly historic piece of legislation."

Rostenkowski also was optimistic, saying each bill "is far more fair and more rational than present law." But he also noted the difficulties conferees will face in the coming weeks as they pit their desire to restore deductions against the need to raise revenues to pay for reducing tax rates.

Even on the first day, conferees did not hesitate to spell out which tax breaks they wish to protect. Senate Majority Leader Robert J. Dole (R-Kan.) called for making tax-rate cuts effective at the same time as limitations on deductions, rather than six months later. Rep. John J. Duncan (R-Tenn.) called for fair treatment of farmers and energy producers. Sen. Malcolm Wallop (R-Wyo.) said he does not want to destabilize the already-weak economy. Rep. J.J. (Jake) Pickle (D-Tex.) seeks to preserve the full deduction for Individual Retirement Accounts and tax-exempt bonds.

The only action any of the committee members took yesterday concerned tax-exempt bonds: Rostenkowski, Packwood and Baker issued a statement effectively closing a loophole that had let states and localities issue tax-exempt bonds even if the projects did not yet need the money, while letting underwriters of the bonds earn interest on the proceeds.